Enhancement mode pseudomorphic high electron mobility transistors (E-pHEMTs) provide operating properties suited for portable wireless applications, such as radio frequency applications. E-pHEMTs require less power to operate than other comparable devices, and consequently, can be used to produce power amplifiers with an exceptional power-added efficiency, which is a measure of how much power is needed to achieve a given amount of amplification. Furthermore, in contrast to other similar devices, E-pHEMTs can operate from a single positive voltage supply since the E-pHEMTs do not require negative gate voltage for control. Thus, E-pHEMTs can be operated without components that provide a negate voltage supply, which translates into decrease in system cost, reduced board space requirements and less complex system design. Due to these operating properties, E-pHEMTs are currently used in radio frequency integrated circuits (RFICs) for portable wireless devices, such as cellular phones.
An importance consideration for designing an RFIC with E-pHEMTs is on-chip electrostatic discharge (ESD) protection. In conventional silicon-based ICs, on-chip ESD protection may be provided by large ESD protection devices, such as capacitors or diode arrays that are specifically included in the ICs for ESD protection. However, due to the high costs associated with the manufacturing of RFICs with E-pHEMTs, the use of large on-chip ESD protection devices in the RFICs is not practical. Even if manufacturing costs are ignored, the demand for smaller RFICs prohibits the use of large on-chip ESD protection devices.
In view of these concerns, what is needed is an IC with E-pHEMTs having on-chip ESD protection and method for fabricating the IC without significantly increasing the overhead on the chip area for the ESD protection.